Updates list of temporarily unspendable outputs.
Temporarily lock (unlock=false) or unlock (unlock=true) specified transaction outputs.
If no transaction outputs are specified when unlocking then all current locked transaction outputs are unlocked.
A locked transaction output will not be chosen by automatic coin selection, when spending bitcoins.
Locks are stored in memory only. Nodes start with zero locked outputs, and the locked output list
is always cleared (by virtue of process exit) when a node stops or fails.
Also see the listunspent call